Polysubstance use, treatment completion, and contact with the justice system: a multistate analysis of treatments for substance use disorders between 2010-2019 in Chile

A. González-Santa Cruz1, 2, , J. Ruiz-Tagle Maturana1, 3, , M. Mateo Piñones1, 4, , A. Castillo-Carniglia5,


1 Young Researcher, Millennium Nucleus for the evaluation and analysis of Drug Policies
2 Ph.D. student, School of Public Health, Universidad de Chile
3 Ph.D. student, Programa de Doctorado en Políticas Públicas, Universidad Mayor, Santiago, Chile.
4 Ph.D. student, Griffith University, Australia
5 Director, Millennium Nucleus for the evaluation and analysis of Drug Policies; Associate Professor, Society & Health Research Center

Background

  • Substance use disorders(SUD) often occur with criminality & contact with the justice system(CJS)
  • People with polysubstance use (PSU) has shown more contacts with the CJS.
  • Completing SUD treatment can help reducing the risk of contacts with the CJS, but not quite clear in people with PSU.
  • More research is needed to understand the link between PSU, treatment completion, and contact with the CJS, specially in Latin America.

    • Objectives: Estimate the effects of PSU at baseline (vs. single substance use) on the probabilities of (i) completing baseline drug treatment and (ii) contacting with the CJS after treatment at 6 months, 1-, 3- & 5-years follow-ups.

    Methods

    Design: retrospective cohort based on the administrative data’s record linkage. Data: Chilean substance use treatment programs and Prosecutor’s Office through a deterministic linkage process. Ethics: We are updating an existing ethical approval by the Griffith University GU Ref No: 2022/919.

    Exposure: baseline PSU (using >1 substance at admission to SUD treatment); Mediator: SUD treatment outcome (complete vs. dropout/spelled by misconduct); Outcome: contact with CJS (committing an offense that led to a condemnatory sentence).

  • The research control for a number of confounding variables (listed in Figure 1), and patients are weighted by the inverse probability of PSU(IPW).
  • We described the cumulative incidence rate (x1,000 person-years) of patients with PSU and no PSU and incidence rate ratios(IRR) of treatment completion and contact with CJS, with and without IPWs.
    • Covariate balance

    Figure 1: Covariate balance

  • We used an illness-death multistate structure to estimate transitions from admission to treatment outcome, treatment outcome to contact with CJS, and admission to contact with CJS (not completing treatment) for patients with and without PSU (Figure 2).
    • Multistate scheme

    Figure 2: Multistate scheme

    We calculated the Aalen-Johansen for transition probabilities at 6 months, 1, 3 & 5 years.

    Preliminary Results

    • Before IPWs patients with PSU had lower rates of treatment completion (IRR=0.53 95%CI: 0.51,0.54) and greater rates of contact with the CJS vs. patients with no PSU (IRR=1.68 95%CI: 1.62,1.74).

    • After IPWs: patients with PSU had lower rates of treatment completion (IRR=0.77 95%CI: 0.74,0.8) but greater rates of contact with the CJS vs. patients with no PSU (IRR=1.11 95%CI: 1.06,1.17).

    Table 1: Transition probabilities in states
    Transition Time PSU No PSU
    From admission to contact with CJS 6_mths 2.2 (2.1,2.3) 1.8 (1.7,1.9)
    From admission to contact with CJS 1_yr 7.9 (7.6,8.1) 6.6 (6.4,6.8)
    From admission to contact with CJS 3_yrs 24.4 (24.0,24.7) 20.7 (20.3,21.1)
    From admission to contact with CJS 5_yrs 33.3 (32.8,33.7) 29.5 (29.0,30.0)
    From admission to tr.completion 6_mths 3.1 (2.9,3.2) 4.0 (3.9,4.2)
    From admission to tr.completion 1_yr 14.6 (14.3,14.8) 17.6 (17.3,18.0)
    From admission to tr.completion 3_yrs 23.6 (23.2,23.9) 27.0 (26.6,27.4)
    From admission to tr.completion 5_yrs 21.4 (21.0,21.8) 24.9 (24.4,25.3)
    From tr.completion to contact with CJS 6_mths 3.0 (2.0,4.0) 2.4 (1.3,3.4)
    From tr.completion to contact with CJS 1_yr 8.7 (7.5,9.8) 5.9 (4.8,7.0)
    From tr.completion to contact with CJS 3_yrs 21.1 (20.0,22.3) 16.2 (15.1,17.3)
    From tr.completion to contact with CJS 5_yrs 28.6 (27.4,29.8) 23.0 (21.8,24.2)

    Transition probabilities: People with PSU have higher probabilities of contact with the CJS, both post-admission and post-treatment, vs. those without PSU. Similarly, they are less likely to complete treatment. Treatment completers had lower probabilities of CJS contact vs. non-completers after 3 years since admission.

    Codes & markdowns: https://fondecytacc.github.io/nDP/index_prop_grant23_24

    Discussion

    Treatment completion can reduce the risk of criminal justice involvement, evident at the 3-year point when most users have finished treatment. Further analysis is needed. People with PSU may need enhanced treatment to complete treatments and avoid contact with the CJS.

    Funding sources: This work was funded by ANID -Millennium Science Initiative Program- N° NCS2021_003 (Castillo-Carniglia) and N° NCS2021_013 (Calvo); The authors have no conflict of interest to declare